Realism
Realism is a framework for international relations.
Formulation
'Realism' as a term has changed significantly over time. Most modern realists point to Carr as the origin. Carr himself had an idea of realism that was defined in contrast to utopianism, and included theories like Marxism.
Modern realism is a theory of how states behave. Overly-simplified, states are in single-minded pursuit of self-preservation. There is an embedded prescriptive theory that, given this pattern of behavior, a state should to behave similarly.
Realist theorists diverge on the causes of this pattern of behavior, and on the expected 'equilibrium' states of the world. For example, a defensive realist expects that arms races and mutually assured destruction keep the world locked in stalemate, with great powers expending military power to maintain this status quo (because they benefit most from it). In contrast, an offensive realist expects that great powers will actively undermine a peaceful status quo (because uncertainty trumps any degree of belief in a stalemate).
Reading Notes
The Twenty Years' Crisis: An Introduction to the Study of International Relations, E. H. Carr, 1939
Countering Guerilla Attack, Walt W. Rostow, 1961
The Tragedy of Great Power Politics, John J. Mearsheimer, 2014 (2nd ed.)
Epistemic superimposition: the war in Ukraine and the poverty of expertise in international relations theory, Jan Dutkiewicz and Jan Smolenski, 2023
To help end war in Ukraine, the Quad should back India to engage Russia, Adarsh Badri, 2023